Reviews of Studies of Boundary Layer Transition in Hypersonic Flows Over Axisymmetric and Elliptic Cones Conducted in the CUBRC Shock Tunnels

Abstract

A review is presented of experimental programs that have been conducted in the shock tunnels at CUBRC to investigate the three-dimensional characteristics of laminar, transitional and turbulent boundary layers over axisymmetric and elliptic cones at angle of attack in hypersonic flows. A series of studies were conducted with sharp and blunted slender cones to investigate the three-dimensional characteristics of transitional flows with the emphasis on the asymmetric loads created by these flows. A companion set of measurements were obtained to examine the effects of tripping the boundary layer on these configurations with surface roughness and discontinuities in the nosetip and cone frusta. These studies which were conducted in two different-sized facilities have been compared with measurements made in other facilities, ballistic ranges, and from flight tests. Recent studies have also been conducted on a cone/cylinder flare configuration to be employed in the HIFiRE 1 flight tests and these measurements have been compared to predictions of transition onset, and the levels of heating in laminar, transitional and turbulent flows over the cone section of the model. Measurements have also been made on elliptic cone configurations in the LENS facilities to examine the effects of Mach number, Reynolds number, nosetip bluntness and vehicle incidence on the onset and three-dimensional characteristics of the regions of laminar, transitional and turbulent flow. In these studies, high-frequency thin-film instrumentation was used examined 2Dand 3D-disturbances which precede the transition process, the large-scale, unsteady nature of the transition onset, and the unsteady characteristics of heat transfer through the transition regions. Finally we review the results of preliminary studies conducted to examine boundary layer transition over the HIFiRE 5 configuration. These studies, in which global heat transfer measurements were made with TSP, demonstrated that the transitional flow over this vehicle is controlled by a combination of 2 nd mode, crossflow, and attachment line instabilities.